1. Field of the Invention
The invention relates to an in-vehicle internal combustion engine control device and a control method for am internal combustion engine, which are applied to a vehicle equipped with an internal combustion engine and another power source, other than the internal combustion engine, as devices that transmit power to a drive wheel, and which start the engine while the vehicle is driving.
2. Description of Related Art
An in-vehicle internal combustion engine control device of this type is for example, described in Japanese Patent Application Publication No. 2009-281260 (JP-A-2009-281260). General in-vehicle internal combustion engine control devices, including the one described in JP-A-2009-281260, control a vehicle equipped with both an internal combustion engine and an electric motor as power sources for rotating the drive wheels of the vehicle, that is, a so-called hybrid vehicle (hereinafter, simply referred to as “HV”). In such control devices, when the vehicle starts driving or when the vehicle is driving at a low speed, the internal combustion engine is stopped, and the vehicle drives only on power from the electric power (electric vehicle drive mode; hereinafter, simply referred to as “EV drive mode”). In addition, when the vehicle is accelerating or when the vehicle is driving at a high speed, the internal combustion engine is operated, and the vehicle drives on power from the internal combustion engine in addition to or instead of power from the electric motor (hereinafter, simply referred to as “non-EV drive mode”). Specifically, as shown by the solid line in FIG. 8, an EV drive mode range and a non-EV drive mode range are defined by a vehicle speed V and a required driving force TRQ of the vehicle, and, as the vehicle driving state shifts from the EV drive mode range to the non-EV drive mode range with a change in the vehicle speed V or a change in the required driving force TRQ of the vehicle, the engine is started.
Incidentally, in fuel injection control of a typical internal combustion engine, in order to improve startability, the first-cycle fuel injection amount is set so as to be larger than the second and the following-cycle fuel injection amounts at the time of an engine start. However, when the control device of the above described HV starts the engine while the vehicle is driving, if the first-cycle fuel injection amount is set so as to be larger than the second and the following-cycle fuel injection amounts, the power of the engine steeply varies with combustion of fuel injected in the first cycle to increase the magnitude of vibrations transmitted to the vehicle body. This makes a driver experience a significant uncomfortable feeling.
Then, in the control device of a typical HV, the second-cycle fuel injection amount is set so as to be larger than the first-cycle fuel injection amount at the time of an engine start while the vehicle is driving to suppress a steep variation in the power of the engine. This suppresses an increase in the magnitude of vibrations transmitted to the vehicle body to alleviate driver's uncomfortable feeling.
In addition, in recent years, development of a vehicle that charges a battery with, not only electric power generated by driving a generator with the power of an engine but also electric power supplied from a power supply outside the vehicle, such as a domestic power supply, that is, a so-called plug-in hybrid vehicle (hereinafter, simply referred to as “PHV”), has been proceeding. In the PHV, the charging capacity of the battery is larger than that of a typical HV, so the EV drive mode range is expanded as shown by the alternate long and short dashes line in FIG. 8.
Incidentally, particularly, in the control device of such a PHV, the EV drive mode-range is expanded as compared with the control device of a typical HV, so, as shown, for example, in FIG. 8, when the vehicle speed V is the same, the EV drive mode may be maintained to a further larger required driving force of the vehicle. Therefore, as the vehicle driving state shifts from the EV drive mode range to the non-EV drive mode range, the vehicle driving force at that time increases, and a mount that couples the internal combustion engine to the vehicle body elastically deforms by a large amount because of the reaction force of the driving force. Then, when the engine is started in a state where the mount is elastically deformed by a large amount, that is, in a state where a margin for the mount to suppress transmission of vibrations is small, if the second-cycle fuel injection amount is set so as to be larger than the first-cycle fuel injection amount at the time of the engine start as described above, vibrations due to initial combustion, transmitted to the vehicle body, is not favorably reduced through elastic deformation of the mount. Thus, as the time interval between vibrations due to cranking and vibrations due to combustion of fuel injected in the second cycle extends, driver's uncomfortable feeling may become more significant.
Note that such a phenomenon is not limited to the control device of a PHV but it can occur almost in common to the control device of an HV in which the EV drive mode range is expanded.